Circuit for neutralization of frequency divider chains



May 12, 1953 R. B. WOODBURY 2,638,549

CIRCUIT FOR NEUTRALIZATION OF FREQUENCY DIVIDER CHAINS Filed Dec. 28, 1945 2 Sheets-Sheet l GROUND CUT OFF GRID I2 OF TUBE IO GROUND CATHODE 26 OF TUBE IO GROUND CUT OFF GRID 42 OF TUBE 4-4 OUTPUT POINT 48 INVENTOR ROGER B.WOODBURY RBY ATTORNEY y 1953 R. B. WOODBURY 2,638,549

CIRCUIT FOR NEUTRALIZATION OF FREQUENCY DIVIDER CHAINS Filed Dec. 28, 1945 2 Sheets-Sheet 2 All I. IIIIHVII" GROUND CUT OFF GRID 54 OF TUBE 5a OUTPUT FROM PLATE 52 v V I GROUND cu OFF GRID 30 0F TUBE 76 I I0 OUTPUT A A AT POINT 62 v V INVENTOR ROGER B.WOODBURY BYW ATTORNEY Patented May 12,

, CIRCUIT FOR NEUTRALIZATION OF FRE- l l QUENCY DIVIDER CHAINS" I 3 Roger'B. Woodbury Boston, Mass, assignor, by

mesne assignments, to the United States of America as represented by the Secretary of the Navy Application December 28, 1945, Serial No. 637,745

This invention relates to frequency dividers, and more particularly to series connected fre-' quency dividing blocking oscillators. v

. eries connected blocking oscillators have been developed for frequency dividing or count-' ing down of a series of pips. When blocking cs cillators are connected in this manner interference between the oscillators may result. Means must be provided to neutralize the stages so that the firing of one blocking oscillator will not affect the blocking oscillator preceding it. Heretofore this has been accomplished by using biased-01f amplifiers for coupling between blocking oscillators.

It is an object of my invention to provide means for preventing such interference between blocking oscillators, whichmeans does not require the use of extra tubes, and which uses few components.

It is a further object of my invention, in one form which it may take, to provide a circuit utilizing the output waveform of a blocking oscillator to prevent the following blocking oscillator from affecting its operation whenever said following blocking oscillator fires. It is a still further object of my invention, in another form which it may take, to provide an improved circuitemploying a feedback to neutralize the effect on a preceding circuit when a. blocking oscillator operates.

a To accomplish the foregoing general objects, and more specific objects which hereinafter appear,-my invention resides-in the circuit elements and their relation one to another, as are more particularly described in the following specification. The specification is accompanied by draw,- ings in which: i

Fig. 1 is a diagram showing one method of coupling between stages; v Fig. 2 shows the wave forms and is explanatory of the circuit shown in Fig. 1;

Fig. 3 is a diagram showing arr-other form of my invention; and

Fig. 4 shows the wave forms and explanatory of the circuit shown in Fig. 3. I Referring to both' forms of my invention, as shown in Figs. 1 and 3, the invention comprises a blocking oscillator stage A followed by a second blocking oscillator stage B. Each stage is used for counting down the numberof pulses applied to it and thus provide an overall frequency division equal to product of the individual divisions. When blocking oscillators are connected in series, in such a manner, errors arise due to interaction between adjacent stageswhen they fire. My i n vention prevents or neutralizes this'interaction 5 Claims. (01. 250-3 resistance 20 of the voltage divider made up of between stages, by appropriate special coupling means, generally designated C. The manner in which the two species operate is, however, different,"and will be described hereinafter.

Referring now to the form of my invention shown in Fig. 1, themeans 0 results in stage 3 firing after stage A. is out off, so that feedback from stage B cannot afiect stage A.

The stages A and B include triode tubes I0 and 44, each of which connects from 13-]- through one winding l4a+46a of its associated transformer, to the plate and from the cathode through the other winding (l4b+46b) of the same transformers. to ground. The transformers are so' poled that as the plate of the tube goes negative the cathode of the same tube will also go negative.

Each tube has an RC grid circuit for controlling its bias to control the counting ratio of the stage. The signal is applied at terminal 24 and couplesfrom the first stage through capacitor 38 to the second stage, and is fed out from there at the cathode lead 48. The coupling between blocking oscillator stages is such that the later stage will not fire until the preceding blocking oscillator stage cuts off.

The operation for this purpose is as follows. The grid 12 of the first tube I0 will try to go pas: tive and cause tube [0 to conduct. When the tube starts conducting the current through transformer winding I ia will increase, which will induce a voltage in the winding 14b, which will drive the cathode lead 26 negative. The grid lead l2 effectively becoming more positive causes grid current to flow and the tube In conducts even heavier. The grid current removes charge from capacitor IE, to make the grid go negative. This action continues until the grid lead 12 of tube Ill reaches the same or a slightly lower voltage than cathode 26. At this point the grid lead I2 of the tube will bevery negative. The grid will now relax toward cut off due to condenser IB discharging, exponentially, toward the positive voltage determined by the setting of tap I8 on resistances 20 and 22.' Positive pulses coming in at terminal 24 will add a series of spikesto' the grid voltage, as shownat 200 in Fig. 2.

After the first two pulses 200 (Fig. 2) occur,

the grid I2 will have risen'high enough so that the next pulse will bring'the grid above cut-off and trigger the tube 10.

This'wave is coupled onto the grid 42 of tube" The waveform 202 v shown in Fig. 2 includes a swing 204 going nega-- 44 through capacitors 38 and 40. The waveform that appears on grid 42 is shown at 202 in Fig. 2. The initial or negative portion 204 of this wave 202', will prevent tube 44 from firing, and then the positiyepqrtiop 29.61 of the-wave 202 will 5 triggertlije t 14' when'l'the gifidiilz is} at af ish. enough potential. Theiirst stage willb'ciit oif by this positive tail 206, and at the same time. the second stage cannot fire until the positive" tail occurs. In this Way the firststage will ,iatlwEtys";v be oif when the latter operates, hen 'theieiwill be no interference. H v I m w Each time the first stageiiifiresXaiter agcertain number of applied pulses 2 .9.; ul efre eeieseinr Fig. 2), the signal 202' described above, will be applied to the grid 42 of tubefl l grid will operate in a manner similartdgfidfl2,"aiid withevery other pulse, in the particular case illus trated in Fig. 2, it too will fire and put out an v nn pw rruls rat i hqwn, tlwi n Fig-U2. 20

borni .mindtha ie the shi ne viding -3':1 an' d the -i-tmeIieeH-ni he-di dingml b us are in ead th said i .o' m y Alth u onl j tw l in s lla e V A ir'isteaifv 0.1"1 changing the relative time n of the: stages; The ignal input also .-ne iv ;puls'es' are: a g 1 9" h 35 e" or tube 58, instead" of positive" pulses be; ma.em 1 e .t the r d. v i t be. 910f Fig;

;.Eachitimie .lt' ibei 58." 111.31 is; nesa iv 121-1 cou le t ou h? e a ci orll th ma, e18 fi eillii. j te .ap fit fnl n dnurr 4n toitlibei Isl w llgfire a i t' i e' p en a ,Thisi p; W f si df sa'lc f ca ad tor l and wer: he s 1 fi tub .1. rpm r iie iie if" y the" signal pips 1ox 'th sia'gi 9 5 wcu a us he catho e: QL IQIL QIQ which o iiicreasihgthe fbias on the" tube. This. lthejtubeigrid 54" to; go more rre'g atiye j gcfhang thedhidfntirfiio oiih? sta .My r itiqnlpr des a means'....1.u-l 50. tfiali mg 1; s intera'ctibn' betwe'enjthe" two stages A d? 'peratibnine at yegpi 'a ejespl ie hrou h a recto-the le ep z' t xtu hese 1,: lses' momentarily .dr pgthev as a p ats 55.

forins; changesf may lRulss appliediitofthe first stage are counted ddwnf-attazjrratio depending on the voltage at tap 5'! and the yalues of resistor 66 and ca- 8 2;. resulting pulses I08 (Fig. 4) ppliTedto'th second stage lower the cathodevolt'age 'oi't t is (Fig. 6), as shown at I08 (Fig. 4) Tube '16 operates like the preceding tube 58". 'Eabh tinre 'it does fire it does so at the san ettime as tube 58, and the applied pulses I08 (Fig. 4) are counted down more. The output l lm is ther taken out ,at cathode 82 (Fig.3)

ivez; This negative si'gnel thecapa'citorl'lz andmight drivewa -mamas of th'ej stage, and affect-theaccuracy-of the wliolesystemlfl V 1 4 To neutraliie '"the' e'iiect of such a reeaithrough capacitor "12 I have provided another cap itori fln tied' between thefplate 18' of tiibe njandfthegri "st r tuiie Negative purses fr' mf plate 'l8Wi1lf nowfbe"fe back re the gi'id 54 '0f "tllb 5B through -capacitors' 10*airid*8l These pulseswill lower thegrid voltage 554 pgneutralize} the effect or tne dtuee feed back" t t plate 52 demise- 58. This tralizati'onus per' forriiejd such a- -w'a'y" charms stage all-operate together -so -ther is no ap preciablechange in-- the p'hase oi the" output a s It sii m te Homem1m mietiiet atlthough the circuit s illustrated se dividingat ai ratiops #41221 ajndZ l, other ratios niay b'e employed in actual practice. Moreover, although only two vplcciing oscillator stages are a g'reater number'- of "series nh ttea rre-mency dividiiig blocking oscillatorsffiihalyf e; ;used ana -may be protected againstundesired nteractl'on as abuve described; I :is believed-"thafithe construction and' oper ati asiwell as the advantages of 'my improved frequency divider circuits-will heapparnt frontthe foregoing detailed n descriptiof f thereof. will also be apparent that" while I have shown and described my invention inseverai -m err eu be tirade ,1 the circuits. disclosed without' departingfroin the-spirit of t'h invention, as sought cobdefined in"- the foilo'wing clain s. v

What" is claiinediisfv ,7 1. A frequenc;,r d amg';i 1-cmttennis gr t;

- in ality 'f's n h oniz'e e blocking*osdillatorsiin second-"tube .1 s 611mm; its plate said series to the frequency control circuit of the preceding oscillator in said series to neutralize the effect of the operation of each oscillator on the preceding oscillator in said series.

2. A frequency dividing circuit comprising a plurality of synchronized blocking oscillators in series, each of said blocking oscillators comprising an electron tube having at least an anode, a cathode and a control grid, a transformer having the primary thereof connected between said anode and a source of anode potential and the secondary thereof connected between said cathode and a point of reference potential and a bias circuit coupled to said control grid, said bias circuit being adapted to bias said grid negatively with respect to said cathode upon conduction through said electron tube and to cause the potential of said grid to rise with time in the absence of conduction through said electron tube, means coupling said anode in each of said oscillators to the anode in the following oscillator in said series and means coupling the anode in each of said oscillators to the bias circuit of the preceding oscillator to neutralize the effect of operation of each of said oscillators on the preceding oscillator in said series,

3. A frequency dividing circuit comprising a plurality of synchronized blocking oscillators connected in series, each of said oscillators comprising an electron tube having at least a grid, a cathode and an anode, a transformer, said transformer having a rimary winding connected from said anode to a source of anode potential and a secondary winding connected from said cathode to a point of fixed reference potential, a first capacitor having one terminal thereof connected to said grid, a relatively low impedance connecting a second terminal of said first capacitor to said point of reference potential, and a relatively high resistive impedance coupling said grid to a source of positive potential, said series connection comprising capacitive coupling means coupling the said anodes in successive oscillator circuits and additional capacitive coupling means coupling the said anode in each oscillator circuit to the junction of said first capacitor and said low impedance means of the preceding oscillator in said series and means for coupling a periodic series of pulses to the first blocking oscillator in said series.

4. A frequency dividing circuit comprising a plurality of blocking oscillators in series, each of said blocking oscillators comprising an electron tube having at least an anode, a cathode and a control grid, a transformer having the primary thereof connected between said anode and a source of anode potential and a secondary thereof connected between said cathode and a point of reference potential, a first capacitor having one terminal thereof connected to said grid, a relatively low impedance connecting a second terminal of said first capacitor to said point of reference potential, and a relatively high resistive impedance coupling said grid to a source of positive potential, means coupling a pulse output signal from one winding of said transformer of each blocking oscillator in said series to a point in the following oscillator of said series at which said pulse signal will initiate the operation of said following oscillator, and means for coupling a periodic pulse signal to the grid of the first oscillator in said series.

5. A frequency dividing circuit comprising a plurality of synchronized blocking oscillators connected in series, each of said oscillators comprising an electron tube having at least a grid, a cathode and an anode, a transformer, said transformer having a primary windin connected from said anode to a source of anode potential and a secondary winding connected from said cathode to a point of fixed reference potential, a first capacitor having one terminal thereof connected to said grid, a relatively low resistive impedance connecting a second terminal of said first capacitor to said point of reference potential, a voltage divider having an adjustable tap, said voltage divider being coupled between said point of reference potential and a point of positive potential, and a relatively high resistive impedance coupling said grid to said tap on said voltage divider, said series connection comprising capacitive coupling means coupling the said anodes in successive oscillator circuits and additional capacitive coupling means coupling said anode in each oscillator circuit to the junction of said first capacitor and said low impedance means of the preceding oscillator in said series and means for coupling a periodic series of pulses to the first blocking oscillator in said series.

ROGER B. WOODBURY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,093,882 Dirks Sept. 21, 1937 2,113,011 White Apr. 5, 1938 2,390,608 Miller Dec. 11, 1945 2,411,573 Holst et al Nov. 26, 1946 2,415,567 Schoenfeld Feb. 11, 1947 2,444,890 Hite et a1 July 6, 1948 2,493,517 Applegarth, Jr Jan. 3, 1950 

